Diversity for air conditioning

[jonboy1]

Hi all, I have a question relating to diversity allowance for air conditioning units (ACU). I have been asked to install 6 no. three phase supplies for acu's in a school.

These have starting 14A Running (max.) 29A each.

Using the on-site guide (an old copy) I have used option 2 as guidance (Heating and power). I calculated total demand at 121 amps with the diversity applied. Can somebody confirm this is correct or is there now an option for ACU's.

Many thanks

Jon

 

[benji]

Have you got the starting /running currents the wrong way round

yours benji

 

[jonboy1]

This is waht i've been sent from the a/c guys. I have accounted for 29 amp max load

 

[controlman]

Diversity is down to the design engineer
Are the units heat pumps - which mean they will run in Winter
Are they all starting together
The starting currents on a AC unit are very short ( not like a SD fan)
Get the correct data RC & SC and the time of the start from the AC guys
Then plot them into the current time graph of the supply breaker/breaker to ensure they will not trip

 

[ian.settle1]

In my opinion there should not be any diversity as depending on the weather they can be running continously. Whether it is heating or cooling.

 

[controlman]

If running current of each unit is 14amp x 6 = 84amp total run current
I think what jonboy is concerned about is the total starting current which you cannot apply diversity to, if they all start at once.
you can apply diversity to only the SC if you staged the starting of them but that would not be practical in their use
eg they would probably have independant control loops
so I agree with ian.settle